Abstract
This paper presents PYFLOW_2.0, a hazard tool for the calculation of the impact parameters of dilute pyroclastic density currents (DPDCs). DPDCs represent the dilute turbulent type of gravity flows that occur during explosive volcanic eruptions; their hazard is the result of their mobility and the capability to laterally impact buildings and infrastructures and to transport variable amounts of volcanic ash along the path. Starting from data coming from the analysis of deposits formed by DPDCs, PYFLOW_2.0 calculates the flow properties (e.g., velocity, bulk density, thickness) and impact parameters (dynamic pressure, deposition time) at the location of the sampled outcrop. Given the inherent uncertainties related to sampling, laboratory analyses, and modeling assumptions, the program provides ranges of variations and probability density functions of the impact parameters rather than single specific values; from these functions, the user can interrogate the program to obtain the value of the computed impact parameter at any specified exceedance probability. In this paper, the sedimentological models implemented in PYFLOW_2.0 are presented, program functionalities are briefly introduced, and two application examples are discussed so as to show the capabilities of the software in quantifying the impact of the analyzed DPDCs in terms of dynamic pressure, volcanic ash concentration, and residence time in the atmosphere. The software and user’s manual are made available as a downloadable electronic supplement.
Highlights
Dilute pyroclastic density currents are turbulent multiphase gravity flows that can occur during explosive volcanic eruptions
The software and user’s manual are given in the electronic supporting material linked to the paper (Electronic Supplementary Material: Folder = PYFLOW_2.0)
A new tool has been included for quantifying the deposition rate and time of the flow, providing a way to estimate the volcanic ash residence time in the air, which can have a significant impact on potentially exposed human beings and animals
Summary
Dilute pyroclastic density currents (hereafter DPDCs) are turbulent multiphase gravity flows that can occur during explosive volcanic eruptions. This part is generally attributed to the particles settling from turbulent suspension (Branney and Kokelaar 2002; Dellino et al 2004, 2008; Sulpizio and Dellino 2008; Sulpizio et al 2016). Given the vertical density stratification and that the fluid phase is a mixture of hot gas and entrained atmospheric air that is less dense than the surrounding atmosphere (Engwell et al 2016), DPDCs develop a basal part with a
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